U.S. patent application number 09/770233 was filed with the patent office on 2002-05-23 for device and method for optical measurement.
Invention is credited to Jonasson, Tomas, Leide, Erlan, Wedelsback, Hakan, Wihlborg, Nils, Ylikangas, Roger.
Application Number | 20020060790 09/770233 |
Document ID | / |
Family ID | 20281877 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020060790 |
Kind Code |
A1 |
Leide, Erlan ; et
al. |
May 23, 2002 |
Device and method for optical measurement
Abstract
A device for optical measuring of small particles for analysis
of the quality of the particles comprises a sample-feeding carrier
which is adapted to take up particle samples in sample holders and
transport the particle samples to a place for optical measurement,
a mirror-supporting means which follows the movement of the carrier
and has mirrors matching the sample holders, a device for
illuminating a particle sample when positioned for optical
measurement and a detector, which is sensitive to electromagnetic
radiation and records at least one result of an optical measurement
of the illuminated particle sample. A mirror of the
mirror-supporting means reflects the particle sample, so that a
mirror image thereof stands essentially still seen from the
detector, when a measurement is being recorded, owing to the fact
that the mirror image of the particle sample falls on a center axis
of the movement of the mirror-supporting means. A method for
optical measuring of small particles uses the device above. The
method comprises the steps of feeding particle samples to a place
for optical measurement, following the movement of a particle
sample with a mirror in such manner that, in the place for optical
measurement, a mirror image of the particle sample falls on a
center axis of the movement of the mirror, illuminating the
particle sample when this is positioned for optical measurement,
and recording at least one result of an optical measurement of the
illuminated particle sample by means of a detector sensitive to
electromagnetic radiation.
Inventors: |
Leide, Erlan; (Helsinborg,
SE) ; Wihlborg, Nils; (Helsinborg, SE) ;
Wedelsback, Hakan; (Angelholm, SE) ; Jonasson,
Tomas; (Helsinborg, SE) ; Ylikangas, Roger;
(Rydeback, SE) |
Correspondence
Address: |
BROWDY AND NEIMARK, P. L. L. C.
624 Ninth Street, N. W.
Washington
DC
20001
US
|
Family ID: |
20281877 |
Appl. No.: |
09/770233 |
Filed: |
January 29, 2001 |
Current U.S.
Class: |
356/244 |
Current CPC
Class: |
G01N 15/147
20130101 |
Class at
Publication: |
356/244 |
International
Class: |
G01N 021/01 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2000 |
SE |
0004534-1 |
Claims
What we claim and desire to secure by Letters Patent is:
1. A device for optical measuring of small particles, such as
grains from cereals and like crops, for analysis of the quality of
the particles, which comprises a sample-feeding carrier which is
adapted to take up particle samples, which each comprise at least
one particle, in sample holders and transport the particle samples
to a place for optical measurement, a mirror-supporting means which
follows the movement of the carrier and has a mirror for each
sample holder, a device for illuminating a particle sample when
this is positioned for optical measurement, and a detector which is
sensitive to electromagnetic radiation for recording at least one
result of an optical measurement of the illuminated particle
sample, a mirror in the mirror-supporting means reflecting the
particle sample so that a mirror image of the particle sample
stands essentially still seen from the detector, when the
measurement is being recorded, owing to the fact that the mirror
image of the particle sample falls on a center axis of the movement
of the mirror-supporting means.
2. The device as claimed in claim 1, wherein the sample-feeding
carrier is adapted to feed the particle samples during continuous
movement.
3. The device as claimed in claim 1, wherein the detector is an
image-recording means which records an image of the particle sample
in the optical measurement.
4. The device as claimed in claim 3, further comprising a means for
image analysis of the recorded image, an image of a particle
sample, which comprises a plurality of particles, being, with the
aid of the means for image analysis, divisible into images of one
particle each.
5. The device as claimed in claim 3, wherein the image-recording
means is a digital camera.
6. The device as claimed in claim 1, wherein the sample holders are
adapted to take up only one particle.
7. The device as claimed in claim 1, wherein the carrier is
circular and rotates to feed the particle samples.
8. The device as claimed in claim 7, wherein the mirror-supporting
means and the carrier are interconnected by a center shaft and thus
follow each other's movements.
9. The device as claimed in claim 1, wherein the mirrors in the
mirror-supporting means are arranged at an angle of 45.degree. to
the center axis, the distance between the particle sample and the
associated mirror being the same as the distance between the mirror
and the center axis for the mirror image of the particle sample to
fall on the center axis.
10. The device as claimed in claim 1, wherein the sample holders of
the carrier comprise indentations which offer a space for a
particle sample.
11. The device as claimed in claim 1, wherein the sample holders of
the carrier comprise through holes in the carrier and a lower
particle holding disk which prevents the particles from falling
through the holes, the holes and the particle holding disk thus
offering a space for a particle sample.
12. The device as claimed in claim 1, further comprising a means
for generating a subatmospheric pressure on the underside of the
carrier, the sample holders of the carrier comprising holes to
which particle samples adhere by means of the subatmospheric
pressure.
13. The device as claimed in claim 1, wherein a plurality of places
for optical measurement are arranged, which each have a detector,
the illumination being variable between the places for different
analyses.
14. A method for optical measuring of small particles, such as
grains from cereals and like crops, for analysis of the quality of
the particles, comprising the steps of feeding particle samples
which each comprise at least one particle, to a place for optical
measurement, following the movement of a particle sample with a
mirror in such manner that, in the place for optical measurement, a
mirror image of the particle sample falls on a center axis of the
movement of the mirror, illuminating the particle sample when
positioned for optical measurement, and recording at least one
result of an optical measurement of the illuminated particle sample
by means of a detector which is sensitive to electromagnetic
radiation, the mirror image of the particle sample standing
essentially still seen from the detector, when the measurement is
being recorded, owing to the fact that the mirror image of the
particle sample falls on the center axis of the movement.
15. The method as claimed in claim 14, wherein the particle samples
are fed during continuous movement.
16. The method as claimed in claim 14, wherein the detector is an
image-recording means which records an image of the particle sample
in the optical measurement.
17. The method as claimed in claim 16, further comprising the step
of dividing an image of a particle sample which comprises a
plurality of particles, into images of one particle each.
18. The method as claimed in claim 16, further comprising the step
of analyzing the recorded image by image analysis for determining
the quality of the particle sample.
19. The method as claimed in claim 16, wherein a digital camera is
used as the image-recording means.
20. The method as claimed in claim 14, wherein only one particle is
fed in each particle sample.
21. The method as claimed in claim 14, wherein the particle samples
are fed by sample holders in a circular carrier, which is rotated
to feed the particle samples.
22. The method as claimed in claim 21, wherein a mirror-supporting
means, which supports mirrors, which follow particle samples, is
connected to the carrier via a center shaft and thus made to follow
the movements of the carrier and the particle samples.
23. The method as claimed in claim 22, wherein the mirrors of the
mirror-supporting means are arranged at an angle of 45.degree. to
the center axis, the distance between a particle sample and the
associated mirror being the same as the distance between the mirror
and the center axis for the mirror image of the particle sample to
fall on the center axis.
24. The method as claimed in claim 21, wherein the sample holders
of the carrier comprise indentations which offer a space for a
particle sample.
25. The method as claimed in claim 21, wherein the sample holders
of the carrier comprise through holes in the carrier and a lower
particle holding disk which prevents the particles from falling
through the holes, the holes and the particle holding disk thus
offering a space for a particle sample.
26. The method as claimed in claim 21, wherein a means for
generating a subatmospheric pressure is arranged on the underside
of the carrier, the sample holders of the carrier comprising holes
to which particle samples are made to adhere by the subatmospheric
pressure.
27. The method as claimed in claim 14, further comprising the step
of recording a plurality of optical measurements of each particle
sample with different kinds of illumination during the
measurements, the recordings occurring in different places by means
of a plurality of detectors.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method and a device for optical
measuring of small particles, such as grains from cereals and like
crops, for analysis of the quality of the particles.
BACKGROUND ART
[0002] Inspection of different kinds of cereals and other crops is
today made all over the world to determine the quality of the
cereals in commercial transactions and handling. The inspection
aims at examining a selected representative sample from a large
consignment and determining the presence of non-desirable grains
and particles. The non-approved grains and particles are classified
and the quantity of each class is determined. Owing to the
distribution of the various grains, the sample and, thus, the
consignment will be given a grading which is a decisive factor in
connection with payment and handling of the consignment.
[0003] Today most cereal inspections are carried out entirely
manually. A skilled inspector has often passed through a
comprehensive education of many years. Nevertheless there are great
deviations in the analyses/classifications between different
inspectors owing to, among other things, personal assessments and
varying conditions of lighting. Deviations also occur in each
individual inspector because of, for example, the degree of
fatigue.
[0004] It is therefore desirable for the methods of analysis to be
automated to reduce the deviations and create a more stable
situation with a more transparent grading process. For an exact
grading of the sample, the grains must be separated from each other
to allow each individual grain to be classified. This can be made
either by physical separation or by means of digital image
processing.
[0005] Thus, use is presently made of certain optical measuring
methods for analysis of the quality of the grains. These measuring
methods are based on a grain being illuminated, whereupon some sort
of detection is made of the light emitted from the grain for
analysis of the quality of the grain. The illumination may vary
significantly regarding, for example, from which direction the
grain is illuminated, which wavelength is used, etc. The detection
may vary in respect of whether e.g. reflected light, transmitted
light or diffuse light is detected.
[0006] Instruments using one or more of these optical measuring
methods have some kind of physical sorting out of the grains so
that only one grain at a time is measured. It should, however, not
be necessary to interrupt the feeding of grains each time a grain
is to be measured. This means that it must be possible to optically
measure moving grains. This places great demands on the optical
detection to prevent the movement of the grain from spoiling the
measurement. An extremely quick detector must be used, which causes
great costs, or the feeding of samples must be carried out so
slowly that a less expensive, slower detector will manage, which
results in a long time of waiting between measurements of two
grains.
[0007] A quick detector also involves peripheral equipment, which
requires a great deal of space. Since the time of exposure must be
very short, the detector also requires that large amounts of light
be available, and this requirement is difficult to satisfy.
[0008] To prevent movement blur from arising, a grain cannot move
more than extremely marginally during the measuring time of the
detector. The measuring time of the detector and the distance a
grain can move during the measurement thus decide the speed at
which the samples can be fed. For an ordinary detector, this means
a very low speed and unacceptable analyzing times.
[0009] A compromise could be to vary the speed of the feeding, in
such manner that the grains are fed quickly when no measurement
occurs, and slowly during measurement. This, however, causes wear
on mechanical components feeding the samples since acceleration and
retardation occur constantly. This also places demands on the
control so that the correct speed is kept up during and between
measurements.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a quick
automatic method for optical measurement of particles for analysis.
A further object is to solve the above problems and provide optical
measurements of particles fed at a high speed, using conventional,
relatively inexpensive detectors.
[0011] The objects of the invention are achieved by means of a
device according to claim 1 and a method according to claim 14.
Further advantages of the invention are evident from dependent
claims 2-13 and 15-27.
[0012] Thus, the invention provides a device for optical measuring
of small particles, such as grains from cereals and like crops, for
analysis of the quality of the particles. The device comprises a
sample-feeding carrier, which is adapted to take up particle
samples, which each comprise at least one particle, in sample
holders and transport the particle samples to a place for optical
measurement, a mirror-supporting means, which follows the movement
of the carrier and has a mirror for each sample holder, a device
for illuminating a particle sample when this is positioned for
optical measurement, and a detector which is sensitive to
electromagnetic radiation for recording at least one result of an
optical measurement of the illuminated particle sample. A mirror in
the mirror-supporting means reflects the particle sample, so that a
mirror image thereof stands essentially still seen from the
detector, when the measurement is being recorded, owing to the fact
that the mirror image of the particle sample falls on a center axis
of the movement of the mirror-supporting means.
[0013] This design implies that the time of exposure can be
extended significantly in the detector since the mirror image of
the particle stands still. The extended time of exposure then
causes no problems with movement blur and conventional detectors
can be used. Particles can thus be fed at a high speed, which
results in a high measuring speed. By the mirror image standing
essentially still is meant that no translational movement occurs,
but only a small degree of turning of the mirror image, owing to
the movement of the mirror in front of the detector. This turning,
however, is so small that no or very little movement blur
arises.
[0014] According to a preferred embodiment, the sample-feeding
carrier is adapted to feed the particle samples during continuous
movement.
[0015] Since the particles can be fed at a high speed without
causing movement blur in the detector, there is no need for a
higher feeding speed between the measurements. The continuous
movement means that the wear on mechanical components in the device
is insignificant.
[0016] The detector is preferably an image-recording means, which
records an image of the particle sample in the optical measurement.
An image contains such an amount of information about the particle
sample that it can be analyzed in respect of several properties on
the basis of one measurement.
[0017] The device advantageously comprises a means for image
analysis of the recorded image, an image of a particle sample,
which comprises several particles, being divisible, with the aid of
the means for image analysis, into images of one particle each. As
a result, several particles can be analyzed on the basis of one
image. The device will not be dependent on the condition that only
one particle at a time is fed to the optical measurement.
[0018] The image-recording means conveniently is a digital camera.
This means that an image of whole particles is recorded and image
analysis can be used to analyze parts of the particles. No
averaging as regards the light from the particle occurs, which
could conceal defects or make the discovery of defects difficult.
The digital camera produces an image in digital format, which is
needed for the image analysis.
[0019] According to a preferred embodiment, the sample holders are
adapted to take up only one particle. This means that a physical
separation of the particles is obtained. In case of several
analyses of the same particle using different illumination
techniques, a physical separation is preferred.
[0020] The carrier is preferably circular and rotates to feed the
particle samples. This ensures easy feeding of samples, and the
feeding frequency can easily be made constant.
[0021] According to a further preferred embodiment, the
mirror-supporting means and the carrier are interconnected by a
central shaft and thus follow each other's movements. This means
that exact following of the movements of the particle samples can
easily be provided. Exact following is important for the mirror
image to stand still on the center axis of the movement.
[0022] The mirrors in the mirror-supporting means are preferably
arranged at an angle of 45.degree. to the center axis, the distance
between the particle sample and the associated mirror being the
same as the distance between the mirror and the center axis for the
mirror image of the particle sample to fall on the center axis. As
a result, the detector is oriented perpendicular to the center axis
for it to perceive the mirror image of the sample on the center
axis. This provides a good position of the detector, which can then
easily be adjusted correctly in terms of angle and which can also
use the same stand as the carrier and the mirror-supporting
means.
[0023] The sample holders of the carrier conveniently comprises
indentations which offer a space for a particle sample. Thus the
particles fall into the indentations when positioned under the
particles. This results in an easy way of taking up particles in
the sample holders.
[0024] According to a preferred embodiment, the sample holders of
the carrier comprise through holes in the carrier and a lower
particle holding disk which prevents the particles from falling
through the holes, the holes and the particle holding disk thus
offering a space for a particle sample. Also this embodiment
results in an easy way of taking up particle samples in the sample
holders. Moreover, the sample holders can easily be emptied by an
emptying hole being arranged in the particle holding disk. When a
full sample holder arrives at the emptying hole, the particle
sample falls out of the sample holder by there being no bottom in
the sample holder any longer.
[0025] According to another embodiment, the device has a means for
generating a subatmospheric pressure on the underside of the
carrier, the sample holders of the carrier comprising holes to
which particle samples are made to adhere by the subatmospheric
pressure. This means that a hole cannot possibly take up a
plurality of particles at a time, which ensures the feeding of only
one particle at a time.
[0026] A plurality of places for optical measurement, which each
have a detector, are advantageously arranged in the device, and the
illumination can be varied between the places for different
analyses. This means that the particles can be analyzed in respect
of several different properties in the same sorting out of the
particles. The advantages of the device having a long time of
exposure in spite of a high feeding speed can be used in all
recordings of images.
[0027] The objects of the invention are also achieved by a method
for optical measuring of small particles, such as grains from
cereals and like crops, for analysis of the quality of the
particles. The method comprises the steps of feeding particle
samples which each comprise at least one particle, to a place for
optical measurement, following the movement of a particle sample
with a mirror in such manner that, in the place for optical
measurement, a mirror image of the particle sample falls on a
center axis of the movement of the mirror, illuminating the
particle sample when located in the place for optical measurement,
and recording at least one result of an optical measurement of the
illuminated particle sample by means of a detector which is
sensitive to electromagnetic radiation. The mirror image of the
particle sample stands essentially still seen from the detector,
when the measurement is being recorded, owing to the fact that the
mirror image of the particle sample falls on the center axis of the
movement. The method provides an automatic technique of recording,
quickly and with conventional detectors, results of optical
measurements for analysis of particles. The particles can be fed at
a high speed, without making it too difficult for conventional
equipment to satisfy the requirements as to a minimum time of
exposure in the detector.
[0028] The method preferably comprises the step of analyzing the
recorded image by means of image analysis to determine the quality
of the particle sample. This means that the analysis can occur
directly in the recording of the image, and a sample result can be
obtained from the device, quickly and on the spot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] A presently preferred embodiment of the invention will now
be described by way of example with reference to the accompanying
drawings.
[0030] FIG. 1 is a perspective view of a sample-feeding carrier and
a mirror-supporting means according to the invention.
[0031] FIG. 2 is a perspective view of a stand in which the carrier
and the means in FIG. 1 can be mounted.
[0032] FIG. 3 is a schematic view and illustrates a recording of a
mirror image of a particle.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0033] FIG. 1 shows a sample-feeding unit 1, which comprises a
sample-feeding carrier 2 in the form of a disk and a
mirror-supporting means 3. These are interconnected by a central
shaft 4, which makes their movements synchronized. The carrier 2 is
adapted to feed the particles 5 which are to be analyzed to a place
where an image of the particle 5 can be recorded.
[0034] Sample holders 6 in the form of holes are arranged along the
outer edges of the carrier 2 and adapted to take up particles 5
which are to be analyzed. For each hole 6, there is a matching
mirror 7, which is placed on the mirror-supporting means 3 in such
manner that a mirror image of a particle 5 in the hole 6 is
projected onto a center axis of the mirror-supporting means 3. The
mirrors 7 are plane and arranged at an angle of 45.degree. to the
center axis, which means that the mirror image of the particle 5 is
turned through 90.degree. .
[0035] The carrier 2 can be dismounted from the central shaft 4 to
be replaced by other carriers 2. This allows adaptation to
different kinds of crops by the carrier 2 being exchanged. The
sample holders 6 on each carrier 2 are then adapted to a certain
kind of crop.
[0036] The carrier 2 and the mirror-supporting means 3 are circular
and rotate in operation about their common shaft 4 for the feeding
of samples. The sample-feeding unit 1 is mounted to rotate in a
stand 8 which is illustrated in FIG. 2. The rotation is driven by a
motor 9 which is mounted on the stand 8.
[0037] Particles 5 falling into the holes 6 in the carrier 2 abut
against a particle holding disk 10, which prevents the particles 5
from falling through the holes 6. The particle holding disk 10 is
therefore arranged immediately below the carrier 2 and thus form a
bottom of the holes 6. The holes 6 are formed as the particles 5
and thus control the orientation of the particles 5 in the holes 6.
This is applicable to, for example, rice, where, for certain
measurements, it is desirable to orient the elongate shape of the
grains correctly. This also facilitates the recording of images
since the image-recording means can easily be set in such manner
that the grains fill the entire surface of exposure.
[0038] A particle 5 which is fed by the continuously rotating
sample-feeding unit 1 is sliding on the particle holding disk 10
during the entire feeding operation. The particle 5 is fed for
optical measurement and is then fed to an emptying hole 11 in the
particle holding disk 10. There the particle 5 falls through the
emptying hole 11 into a collecting vessel.
[0039] The carrier 2 forms an inclined plane, which makes particles
5 that are not taken up in sample holders 6 on the carrier 2, fall
down towards a particle holding pocket, at the bottom of the
inclined plane. The particle holding pocket forms a wall along part
of the circumference of the carrier 2 and prevents the particles 5
from sliding off the carrier 2. A particle 5 abutting against the
wall of the particle holding pocket is positioned at the same
distance as the sample holders 6 from the center of the carrier 2.
All particles in a sample will therefore be taken up by sample
holders 6 as they rotate up to the particle holding pocket.
[0040] When the particles 5 fall through the emptying hole 11, the
sample holder 6 will be empty, and when the carrier 2 is rotated,
the sample holder 6 will then arrive at the particle holding pocket
where a new particle 5 is taken up. Should two particles 5 fall
into the same hole 6, one of them will protrude from the hole 6.
The sample holder 6 passes a brush which sweeps the protruding
particle 5 away from the hole 6. If a particle 5 is broken, it can
be so small that two particles 5 can be taken up in the same hole
6. This problem is solved in the recording of the optical
measurement and will be discussed further below.
[0041] A device for illumination in the form of illuminating means
12 which constitute light sources for illumination of the particles
5 can be mounted in various ways. They can be mounted adjacent to
each sample holder 6 on the carrier 2 in the form of
surface-mounted light emitting diodes or somewhere on the stand 8.
The light source can then be mounted, for example, under the
carrier 2, in which case transmitted light is measured, or adjacent
to a detector 13, in which case reflected light is measured. The
illuminating means 12 can, of course, be any kind of light source
whatever, such as some sort of laser or a gas discharge lamp.
[0042] The detector 13 is mounted on the stand 8 in such manner
that an angle between the direction in which the detector 13 takes
in light, and the plane of a mirror 7 in the mirror-supporting
means 3 is the same as the angle between the plane of the mirror 7
and the center axis. Such a device means that the detector 13 sees
a mirror image of the particle 5 which is projected onto the center
axis. Since the mirror 7 is inclined at an angle of 45.degree. to
the center axis, the detector 13 is arranged in the plane of the
mirror-supporting means 3 and angled to record measurements
perpendicular to the movement, i.e. at an angle of 45.degree. to
the mirror 7.
[0043] The detector 13 suitably is an image-recording means. The
image-recording means 13 is in turn in this embodiment a
conventional CCD camera. The recorded image will then be obtained
in electronic form and can, in the camera, be readily converted
into a digital format, which is needed for the continued image
analysis. Moreover, the image which is recorded in the camera can
be divided into a plurality of images. This is needed if the image
comprises several particles. This image is then divided into a
plurality of images, so that each image comprises one particle
only. Subsequently, the continued image analysis can be carried out
in respect of each particle separately.
[0044] There is also a reference disk 14, which can be put forward
over the carrier 2. The reference disk 14 is operated by a stepping
motor which puts forward test plates on the reference disk 14 to be
recorded in the detector 13. This means that test plates with known
properties can be used to calibrate the detector 13.
[0045] FIG. 3 shows schematically the recording of an image of a
particle 5. The particles 5 are fixed in fixed positions on the
carrier 2 while the particles are transported past the
image-recording means 13. A plane mirror 7 is fixedly arranged
above each particle position at an angle of 45.degree. and rotates
with the carrier 2. The distance between the center of the particle
5 and the mirror 7 (d.sub.1) should be the same as the distance
between the mirror 7 and the center axis of the carrier 2 (d.sub.2)
for the mirror image of the particle 5 to be projected onto the
center axis. The distance to the image-recording means 13 is
determined by the optics used to obtain the desired properties.
[0046] The image-recording means 13, which is fixedly arranged,
sees in this way the mirror image projected onto the center axis of
the carrier 2 during the time when the mirror 7 is in front of the
image-recording means 13. The effect will be a stationary mirror
image for a certain time which is dependent on the speed of
rotation and size of the carrier 2 and the mirror 7. The mirror
image, however, is not quite stationary. The particle 5 is turned
round its center, but the angle of this turning is the same as the
angle through which the carrier 2 is turned during the time when
the mirror 7 is in front of the image-recording means 13. This is
such a small angle that the turning of the particle 5 does not
cause movement blur in an image that is being recorded by the
image-recording means 13.
[0047] The extended time which is now available to collect
measuring data increases significantly, which radically simplifies
the construction for illumination and the other components in the
system. Thanks to the extended time, the detector 13 manages to
make a plurality of optical measurements of the particle 5 during
the time when the particle 5 is in front of the detector.
[0048] Also other optical measuring methods that one wants to
combine with quick feeding of samples can use the solution
described above.
[0049] A method of optical measuring of particles 5 for analysis
will now be described in more detail. A sample which is to be
analyzed is placed in a funnel in the analysis instrument. In most
cases, the sample consists of about 1200 grains or particles (about
30 g), but can be up to 150 g. The sample is then passed down to
the particle holding pocket which is mounted at the opening of the
funnel. The sample mechanism is started and the particles 5 are
separated individually on the carrier 2 and fed to a camera 13.
Here the particle 5 is illuminated and the camera 13 records an
image of the illuminated particle 5. The carrier 2 is rotated in a
continuous movement, but by the arrangement of the
mirror-supporting means 3, which has been described above, a
relatively long time of exposure can be used in the camera 13
without movement blur arising. Then the particle 5 is fed to
further cameras 13, if any, which record images of the particle 5
in different lighting. After all the necessary images of the
particles 5 have been recorded, the sample-feeding unit 1 continues
to feed the particle, which is then released into the collecting
vessel. The recorded images are analyzed to discover defects on the
particles 5, such as discolorations, damage etc. When the analysis
of the sample is completed, after about 1 min, the result is shown
on a display and the operator can empty the collecting vessel. The
result shows statistics of the amount of particles having different
types of damage and the amount that was approved.
[0050] It will be appreciated that a great number of modifications
of the above embodiment are feasible within the scope of the
invention as defined by the appended claims. For instance, the
sample holder of the carrier could be designed in some other
manner. The holes could be so small that a particle cannot fall
therethrough. The particle holding disk would in that case be
replaced by a fan which generates a subatmospheric pressure on the
underside of the carrier. The particles would then be fixed by
suction to the holes by the subatmospheric pressure, and owing to
the holes being small the particles could not fall therethrough.
Moreover, two particles could not stay at one hole since the hole
is smaller than the particles and the subatmospheric pressure
causes the particles to stay with their center over the hole. The
particles having passed the optical measurement, the carrier could
pass a place where there is no subatmospheric pressure under the
carrier. The particles will then fall off from the inclined carrier
into a collecting vessel.
[0051] The sample holders of the carrier could also be formed as
indentations in the carrier. The particles would then fall down
into these indentations and in this manner be advanced to the
optical measurement. The emptying of the sample holders could then
take place by the particles being blown out or being pushed out by
means of a brush.
[0052] Alternatively, thanks to the possibility of dividing an
image of several particles, particle samples comprising a plurality
of particles can be fed on the carrier. A plurality of particles
will then be measured simultaneously, but the image must be divided
into a plurality of images of one particle each.
[0053] According to a further alternative embodiment, the mirrors
of the mirror-supporting means could be arranged at a different
angle to the center axis. The image-recording means would then need
to be dislodged accordingly, so that the mirror image of the
particle stands still seen from the image-recording means.
[0054] The optical measurement can be any kind of light-sensitive
measurement. The detector need not record an image but can record
the light intensity in certain points or some kind of averaging
among a plurality of properties, such as directly reflected light
compared with diffusely reflected light. An image-recording means
could be, for instance, another type of digital camera, such as a
CMOS camera.
[0055] Furthermore the sample-feeding unit need not rotate during
continuous movement, but this is in most cases advantageous since
it causes insignificant wear on mechanical parts.
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